This invention relates to a method for the making of optoelectronic semiconductor devices and more specifically to the making of separate confined superlattice structures prepared from binary III-V compounds.
The growth of semiconductor III-V compounds by chemical vapor deposition (CVD) using organometallics and hydrides as elemental sources has developed into a viable process with many potential commercial applications. The metallo-organic chemical vapor deposition (MOCVD) process, based on the pyrolysis of alkyls of group-III elements in an atmosphere of the hydrides of group-V elements, is a common growth technique because it is well adapted to the growth of submicron layers and heterostructures.
In general, III-V semiconductor alloys in the form of binary, ternary, and quaternary compounds are used when forming semiconductor multi-layer devices. A prime concern is the lattice matching of all adjacent layers. Useful physical properties derive directly from adjacent layers which are properly lattice matched. Lattice constants of these alloys can be determined mathematically. For instance see FIG. 2 of U.S. Pat. No. 5,384,151. For ternary compounds AxB1xe2x88x92xC the bandgap energy Eg(x) varies with the composition X as follows:
Eg(x)=Eg(0)+bx+cx2xe2x80x83xe2x80x83(1)
where Eg(0) is the handgap energy of the lower handgap binary compound, c is the bowing parameter, b is the fitting parameter and xxe2x89xa61. Representative ternary compound bandgaps are as follows. Representative values for b are shown.
xe2x80x83InxGa1xe2x88x92xN Eg(x)=
The lattice constant of ternary alloys can be expressed as
aalloy=xaA+(1xe2x88x92x)aBxe2x80x83xe2x80x83(3)
where aA and aB are the lattice constants of the binary alloys A+B, and xxe2x89xa61.
For quaternary compounds, the lattice parameter a0 of an alloy AxB1xe2x88x92xCyD1xe2x88x92yis:
a0=xyaAC+x(1xe2x88x92y)aAD+(1xe2x88x92x)yaBC+(1xe2x88x92x)(1xe2x88x92y)aBDxe2x80x83xe2x80x83(4)
where x, yxe2x89xa61.
The bandgap energy of a quaternary compound is:
Eg=xy EAC+x(1xe2x88x92y)EAD+(1xe2x88x92x)EBC+(1xe2x88x92x)(1xe2x88x92y)EBDxe2x80x83xe2x80x83(5)
where x, yxe2x89xa61.
The following table shows binary compounds which may be matched to quaternary compounds:
Based on the above, it can be seen that when one is preparing a semiconductor device with quaternary compounds and ternary compounds, the selection of materials becomes all important and limiting to the selection process, particularly when lattice matching is taken into account.
An object, therefore of the subject invention is the growth of high quality semiconductor devices with wavelength ranges from 0.26 to 10 microns.
A further object of the subject invention is a semiconductor utilizing superlattice structures for confinement layers, active layers, and waveguide layers.
A further object of the subject invention is a semiconductor structure formed solely of binary alloy compounds in a superlattice environment.
These and other objects are obtained by the subject invention wherein there is provided a semiconductor device and a method for making such semiconductor device comprising confinement layers, waveguide layers, and active layer, all of which or partially of which are formed of a superlattice structure of binary III-V compounds. Depending on the selection of III-V compounds, lasers which emit at wavelengths of from 0.2 microns to 10 microns may be prepared.